The accused Soho House killer is crying a river on Rikers Island.

Nicholas Brooks, charged with the drowning death of his designer ex-girlfriend in the exclusive club and hotel, has been weeping “like a baby” since getting locked up — with fellow inmates threatening to “mess him up” for murdering a woman, a source told The Post.

Brooks broke down yesterday when he got a jailhouse visit from two women — believed to be his mom and sister — said the source, a visitor who was there to see her inmate relative.

“All he does is cry like a baby and say how he wants to get out of here,” she said.

Brooks — who told cops he feared “getting beat up by white supremacists” in jail — has good reason for getting gushy-eyed.

The witness said Rikers inmates are hankering to hurt Brooks, 24, because of his alleged murder of beautiful swimsuit designer Sylvie Cachay, whose semi-nude corpse was found Dec. 9 in a bathtub in their hotel room.

On a bus ride from Rikers to Manhattan Supreme Court with other inmates Tuesday, “Everybody was taunting him,” said the witness.

“You’re a p – – – y!” the jailbirds jeered.

“How could you kill a woman?

“They were saying, ‘We’re going to mess him up,’ ” the relative said.

“He never said one word back.”